With respect to range measurement using radio wave, that is, a radar function, many technologies have been disclosed so far. For example, radar and the like using a pulse monotonously and repeatedly transmitted as a range function are known.
In recent years, as a radio communication technology of a new concept, an UWB (Ultra Wideband) radio system which is an ultra wideband radio system using a band of several GHz has become the center of attention.
The UWB is an impulse radio system using an ultra short pulse wave having a pulse width of approximately nano seconds or less. Communications can be made by modulating information into the position, the phase, and the amplitude of the impulse.
The UWB radio system has features that, by measuring the time by which the impulse is transmitted and the time until the transmission wave is reflected on a predetermined physical object surface and is received again at a transmission source, the ranging between the predetermined physical object and the UWB wave transmission source can be highly accurately performed.
On the other hand, a device that simultaneously realizes a ranging function and a communication function is being developed, and for example, in Patent Document 1, both of these functions are realized in the same device. In Patent Document 1, when performing data communications using a radio communication device, to avoid interference with the other radio communication and the like, a communication range is decided by using the ranging function in advance, and based on this, a transmission output is decided.
Patent Document 1: Japanese Patent Application Laid-Open No. 2003-174368